The long range goal of the proposed research is to understand the HIV assembly process at a molecular level. The investigator proposes using eukaryotic expression vectors which produce individual viral proteins as well as infectious proviral DNA clones. In some instances, specific mutations in individual proteins involved in assembly will be made and the effect of the mutation on assembly will be examined. Specifically, the applicant is interested in defining, in detail, how HIV core protein precursors interact to form virus particles. He also proposes to study the effect of viral envelope proteins and vpu on virus release and assembly, and to examine the mechanisms which underlie the targeting of viral envelope proteins and core precursors to apposing sites on the plasma membrane. Lastly, the investigator will try to determine in more detail how viral RNA is packaged and to compare the assembly process for HIV-1 to HIV-2 to determine if "phenotypic mixing" between these two viruses can occur.